JP3572938B2 - Electrical steel sheet with excellent sticking and corrosion resistance - Google Patents
Electrical steel sheet with excellent sticking and corrosion resistance Download PDFInfo
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Description
【０００１】
【発明が属する技術分野】
本発明は、主としてモーターやトランス等の鉄芯材料として使用される、表面に絶縁皮膜を有する電磁鋼板に関する。
【０００２】
【従来の技術】
電磁鋼板はモーターやトランス等の鉄芯材料として広く利用されており、通常、渦電流損失を低減するための絶縁皮膜を鋼板表面にコーティングして使用される。
モーターやトランス等の鉄芯の多くは、絶縁皮膜が形成された電磁鋼板を所定形状に打ち抜くか若しくは剪断した後、積層し、この積層体を溶接またはカシメにより固定し、必要に応じて歪取焼鈍を施した後、捲き線を施して製品となる。
【０００３】
このような鉄芯用の材料である電磁鋼板の絶縁皮膜には、絶縁性が高いことに加え、皮膜密着性、溶接性、耐食性、打ち抜き性等に優れていることが要求される。さらに、歪取焼鈍が施される場合には、焼鈍時に鋼板どうしが密着（スティッキング）すると電気的短絡が生じて鉄損が増加する問題を生じることから、焼鈍時に鋼板どうしが密着しないこと、すなわち耐スティッキング性に優れていることが要求される。
【０００４】
従来、このような諸特性を得るために以下のような技術が提案されている。
特開平３−２４０９７０号には、歪取焼鈍後の皮膜特性（耐焼付け性、潤滑性）の優れた電磁鋼板の製造方法として、クロム酸と、Ａｌ、Ｍｇ等の酸化物と、樹脂粒子径が０．２〜０．５μｍの有機樹脂エマルジョン（アクリル、スチレン、酢酸ビニル及び／又はこれらの共重合体樹脂）及び樹脂粒子径が１〜５０μｍの有機樹脂エマルジョン（メチルメタアクリレート、ポリアクリルニトリル、ポリスチレン等の樹脂及び／又はこれらの共重合体樹脂、架橋体樹脂）とからなる処理液を電磁鋼板の表面に塗布し、焼き付けることにより絶縁皮膜を形成する方法が示されている。
【０００５】
特許第２６６２１４８号には、電磁鋼板の表面に、樹脂粒子径０．５〜３．０μｍのエポキシ、スチレン、フェノール、メラミン、ポリエステル、酢酸ビニル、アクリル、シリコン系エマルジョン樹脂の１種又は２種以上と、Ａｌ、Ｍｇ、Ｃａ、Ｚｎのクロム酸塩の１種又は２種以上を主成分とする処理剤が塗布焼付けされて、表面粗さＲａが０．１５〜０．６μｍの絶縁皮膜が形成され、且つ、エマルジョン樹脂により表面に形成される球面状の突起物形状が直径３μｍ以下、高さ３μｍ以下である皮膜特性に優れた無方向性電磁鋼板が示されている。
【０００６】
【発明が解決しようとする課題】
しかし、これらの従来技術には下記のような問題がある。
特開平３−２４０９７０号の技術は、有機樹脂エマルジョンとして粒子径０．２〜０．５μｍの樹脂微粒子に加えて、所定の表面粗さを得るために粒径の大きい粗大樹脂粒子（実質的に数μｍ以上の粒子径を有する樹脂粒子）を使用している。このため添加した粗大樹脂粒子により耐スティッキング性は向上するものの、塩化物イオンが存在するような厳しい腐食環境中での耐食性は劣ったものとなる。また、粗大樹脂粒子の添加による樹脂粒子の凝集や皮膜中での樹脂粒子の不均一化により、皮膜特性が安定しないという問題も生じる。
【０００７】
また、特許第２６６２１４８号の技術は、絶縁皮膜に所定の表面形状を与えるために０．５〜３．０μｍの粒子径の有機樹脂エマルジョンを単独で使用しているが、絶縁皮膜厚が０．５〜０．６μｍ以下の薄膜になった場合、樹脂粒子が欠落して皮膜中に含有されにくくなり、その結果、樹脂粒子によって期待される耐スティッキング性の効果が減少するとともに、欠落部では錆が発生し易くなり、耐食性も著しく劣ったものとなる。特に、近年においてはモーター等の高効率化等の観点から絶縁皮膜は薄膜化する傾向にあり、このような薄膜の絶縁皮膜においては、特許第２６６２１４８号の技術では十分な耐スティッキング性と耐食性は得られない。
【０００８】
したがって本発明の目的は、耐スティッキング性と耐食性がともに優れ、しかも、絶縁皮膜として要求される他の諸特性にも優れた絶縁皮膜を有する電磁鋼板、とりわけ、０．５〜０．６μｍ以下の薄膜の絶縁皮膜を形成した場合にも優れた耐スティッキング性と耐食性が得られる電磁鋼板を提供することにある。
【０００９】
【課題を解決するための手段】
本発明者らは、無機−有機系絶縁皮膜を形成する際の無機成分に配合される有機樹脂エマルジョンの樹脂粒子径に着目し、耐スティッキング性と耐食性がともに優れた絶縁皮膜を得るための条件について種々の実験と検討を行い、その結果以下のような知見を得た。
【００１０】
（１） 絶縁皮膜中に分散させる有機樹脂エマルジョンの樹脂粒子径を大きくすると耐スティッキング性は向上するが、一方で樹脂粒子径が大きくなるにしたがって耐食性は劣化する。
（２） このような問題に対して、絶縁皮膜中に分散させる有機樹脂エマルジョンとして、特定の粒子径を有する微細粒子有機樹脂エマルジョンとこれよりも大きい特定の粒子径を有する有機樹脂エマルジョンとを複合添加することにより、耐スティッキング性と耐食性がともに優れた絶縁皮膜が得られる。
【００１１】
（３） また、これら複合添加する２種類の有機樹脂エマルジョンを特定の割合で配合した場合に、特に優れた耐スティッキング性と耐食性が得られる。
（４） 絶縁皮膜中の無機成分と有機成分の比率を最適化し、且つ無機成分の一部として硼酸及び／又は硼酸塩を添加することにより、耐スティッキング性と耐食性はさらに向上する。
本発明はこのような知見に基づきなされたもので、以下のような構成からなることを特徴とする。
【００１２】
［１］ 電磁鋼板の表面に、無水クロム酸、クロム酸塩、重クロム酸塩の中から選ばれる少なくとも１種と、２価又は３価の金属の酸化物、水酸化物及び炭酸塩の中から選ばれる少なくとも１種を含む無機系水溶液（ａ）と、エポキシ系樹脂、スチレン系樹脂、フェノール系樹脂、メラミン系樹脂、ポリエステル系樹脂、酢酸ビニル系樹脂、ベオバ系樹脂、アクリル系樹脂、シリコン系樹脂の各樹脂エマルジョンの中から選ばれる１種又は２種以上からなり、樹脂粒子径が０．０１〜０．１４μｍである有機樹脂エマルジョン（ｂ１）と、エポキシ系樹脂、スチレン系樹脂、フェノール系樹脂、メラミン系樹脂、ポリエステル系樹脂、酢酸ビニル系樹脂、ベオバ系樹脂、アクリル系樹脂、シリコン系樹脂の各樹脂エマルジョンの中から選ばれる１種又は２種以上からなり、樹脂粒子径が０．６〜１．５μｍである有機樹脂エマルジョン（ｂ２）とを主成分とし、且つ有機樹脂エマルジョン（ｂ １ ）と有機樹脂エマルジョン（ｂ ２ ）の樹脂固形分の配合比が、重量比で有機樹脂エマルジョン（ｂ １ ）／有機樹脂エマルジョン（ｂ ２ ）＝７０／３０〜９０／１０、ＣｒＯ ３ 換算量での無機成分（ａ）１００重量部に対する有機樹脂エマルジョン（ｂ １ ）と有機樹脂エマルジョン（ｂ ２ ）の樹脂固形分での合計の配合量が２０〜５０重量部に調整された処理液を塗布し焼付することにより形成された膜厚０．２〜２．０μｍの絶縁皮膜を有することを特徴とする耐スティッキング性及び耐食性に優れた電磁鋼板。
【００１３】
［２］ 電磁鋼板の表面に、無水クロム酸、クロム酸塩、重クロム酸塩の中から選ばれる少なくとも１種と、２価又は３価の金属の酸化物、水酸化物及び炭酸塩の中から選ばれる少なくとも１種を含む無機系水溶液（ａ）と、エポキシ系樹脂、スチレン系樹脂、フェノール系樹脂、メラミン系樹脂、ポリエステル系樹脂、酢酸ビニル系樹脂、ベオバ系樹脂、アクリル系樹脂、シリコン系樹脂の各樹脂エマルジョンの中から選ばれる１種又は２種以上からなり、樹脂粒子径が０．０１〜０．１４μｍである有機樹脂エマルジョン（ｂ１）と、エポキシ系樹脂、スチレン系樹脂、フェノール系樹脂、メラミン系樹脂、ポリエステル系樹脂、酢酸ビニル系樹脂、ベオバ系樹脂、アクリル系樹脂、シリコン系樹脂の各樹脂エマルジョンの中から選ばれる１種又は２種以上からなり、樹脂粒子径が０．６〜１．５μｍである有機樹脂エマルジョン（ｂ２）と、硼酸及び／又は硼酸塩と、有機還元剤とを主成分とし、且つ有機樹脂エマルジョン（ｂ １ ）と有機樹脂エマルジョン（ｂ ２ ）の樹脂固形分の配合比が、重量比で有機樹脂エマルジョン（ｂ １ ）／有機樹脂エマルジョン（ｂ ２ ）＝７０／３０〜９０／１０、ＣｒＯ３換算量での無機成分（ａ）１００重量部に対する有機樹脂エマルジョン（ｂ１）と有機樹脂エマルジョン（ｂ２）の樹脂固形分での合計の配合量が２０〜５０重量部、硼酸及び／又は硼酸塩の合計の配合量が５〜６０重量部、有機還元剤の配合量が１０〜８０重量部に調整された処理液を塗布し焼付することにより形成された膜厚０．２〜２．０μｍの絶縁皮膜を有することを特徴とする耐スティッキング性及び耐食性に優れた電磁鋼板。
【００１４】
［３］ 上記［１］又は［２］の電磁鋼板において、有機樹脂エマルジョン（ｂ２）の樹脂粒子径が０．６〜１．０μｍであることを特徴とする耐スティッキング性及び耐食性に優れた電磁鋼板。
【００１６】
【発明の実施の形態】
以下、本発明の詳細をその限定理由とともに説明する。
本発明において、絶縁皮膜を形成する基板となる鋼板は、モーターやトランス等の電気機器に利用される鉄芯用の電磁鋼板である。このような電磁鋼板としては、無方向性電磁鋼板や方向性電磁鋼板が一般的であるが、これ以外にも軟鋼板、ステンレス鋼板、その他の特殊鋼板等でもよく、基板となる鋼板は特に限定されない。本発明の効果は、これら何れの鋼板を基板とした場合でも得ることができる。
【００１７】
また、基板となる電磁鋼板は、その表面に予め亜鉛系めっきまたはその他金属めっき皮膜、化成処理皮膜等の表面処理の１種または２種以上を施したものでもよく、本発明において電磁鋼板の表面とは、これら表面処理皮膜を有する場合にはその最上層皮膜の表面を言うものとする。
【００１８】
本発明の電磁鋼板の表面に形成される絶縁被膜は、無水クロム酸、クロム酸塩、重クロム酸塩の中から選ばれる少なくとも１種と、２価又は３価の金属の酸化物、水酸化物及び炭酸塩の中から選ばれる少なくとも１種を含む無機系水溶液（ａ）に、樹脂粒子径が０．０１〜０．１４μｍである特定の樹脂エマルジョンの１種又は２種以上からなる有機樹脂エマルジョン（ｂ１）、樹脂粒子径が０．６〜１．５μｍである特定の樹脂エマルジョンの１種又は２種以上からなる有機樹脂エマルジョン（ｂ２）を配合し、さらに必要に応じて硼酸及び／又は硼酸塩と有機還元剤を配合した処理液を塗布し焼付することにより形成される皮膜である。
【００１９】
処理液中の無機系水溶液（ａ）は、無水クロム酸、クロム酸塩、重クロム酸塩の中から選ばれる少なくとも１種と、２価又は３価の金属の酸化物、水酸化物及び炭酸塩の中から選ばれる少なくとも１種を含む無機系水溶液である。
クロム酸塩及び重クロム酸塩としては、ナトリウム、カリウム、マグネシウム、カルシウム、マンガン、モリブデン、亜鉛、アルミニウム等の塩を用いることができる。
【００２０】
また、水溶液中に溶解させる２価又は３価の金属の酸化物としては、例えばＭｇＯ、ＣａＯ、ＺｎＯ等が、水酸化物としてはＭｇ（ＯＨ）２、Ｃａ（ＯＨ）２、Ｚｎ（ＯＨ）２等が、炭酸塩としてはＭｇＣＯ３、ＣａＣＯ３、ＺｎＣＯ３等が挙げられ、これらを無水クロム酸、クロム酸塩、重クロム酸塩の少なくとも１種を主剤に用いた水溶液に溶解させて、無機系水溶液とする。
これらの無機成分によりクロム化合物を含む無機−有機系絶縁皮膜を形成することができる。
【００２１】
上記無機成分を含む処理液中には、樹脂粒子径が異なる有機樹脂エマルジョン（ｂ１）と有機樹脂エマルジョン（ｂ２）が配合される。
前記有機樹脂エマルジョン（ｂ１）は、エポキシ系樹脂、スチレン系樹脂、フェノール系樹脂、メラミン系樹脂、ポリエステル系樹脂、酢酸ビニル系樹脂、ベオバ系樹脂、アクリル系樹脂、シリコン系樹脂の各樹脂エマルジョンの中から選ばれる１種又は２種以上からなり、且つ樹脂粒子径が０．０１〜０．１４μｍの樹脂エマルジョンであり、また、前記有機樹脂エマルジョン（ｂ２）は、エポキシ系樹脂、スチレン系樹脂、フェノール系樹脂、メラミン系樹脂、ポリエステル系樹脂、酢酸ビニル系樹脂、ベオバ系樹脂、アクリル系樹脂、シリコン系樹脂の各樹脂エマルジョンの中から選ばれる１種又は２種以上からなり、且つ樹脂粒子径が０．６〜１．５μｍの樹脂エマルジョンである。本発明では、このような大きさが異なる特定粒子径の２種類の有機樹脂エマルジョンを複合添加することに大きな特徴がある。
【００２２】
樹脂エマルジョンとして上記有機樹脂エマルジョン（ｂ１）を単独で用いた場合には、積層後の歪取焼鈍時に絶縁皮膜中の有機樹脂自体の凹凸による物理的効果が得られず、歪取焼鈍時に原板自体の粗さに起因した凸部にのみ応力が集中し、この応力集中と焼鈍時の熱により絶縁皮膜が破壊され、スティッキングを生じてしまう。一方、樹脂エマルジョンとして上記有機樹脂エマルジョン（ｂ２）を単独で用いた場合には、特に絶縁皮膜厚が０．５〜０．６μｍ以下の薄膜となると樹脂粒子が皮膜中に取り込まれにくくなり、有機樹脂エマルジョン（ｂ２）で期待される耐スティッキング性の改善効果が著しく低下し、また、皮膜中に有機樹脂エマルジョン（ｂ２）の樹脂粒子が取り込まれても、これが容易に欠落するために皮膜欠陥部が生じ、この結果、耐食性と絶縁性が低下してしまう。
【００２３】
これに対して有機樹脂エマルジョン（ｂ１）と有機樹脂エマルジョン（ｂ２）を複合添加した場合には、耐スティッキング性と耐食性がともに優れた絶縁皮膜を得ることができる。このように大きさが異なる特定粒子径の２種類の有機樹脂エマルジョンを複合添加することにより優れた特性が得られる理由は必ずしも明らかではないが、有機樹脂エマルジョン（ｂ１）と併用することにより有機樹脂エマルジョン（ｂ２）が皮膜中に取り込まれやすくなるためであると考えられる。
【００２４】
有機樹脂エマルジョン（ｂ１）及び有機樹脂エマルジョン（ｂ２）は、エポキシ系樹脂、スチレン系樹脂、フェノール系樹脂、メラミン系樹脂、ポリエステル系樹脂、酢酸ビニル系樹脂、ベオバ系樹脂、アクリル系樹脂、シリコン系樹脂の各樹脂エマルジョンの中から選ばれる１種又は２種以上からなる。これ以外の有機樹脂エマルジョンでは、クロム酸系無機水溶液中での安定性が悪いため、同水溶液中に配合後短時間後で劣化し、ゲル状ブツの発生や処理液全体のゲル化を起こし、実用上問題があるため好ましくない。
【００２５】
有機樹脂エマルジョン（ｂ１）の樹脂粒子径が０．１４μｍ超では、上述したような薄膜の絶縁皮膜を形成する際に、有機樹脂エマルジョン（ｂ２）の樹脂粒子を皮膜中に取り込む効果が十分に得られず、このため耐スティッキング性と耐食性が劣る。また、有機樹脂エマルジョン（ｂ１）のより好ましい樹脂粒子径は０．０１〜０．１４μｍであり、これにより特に優れた耐スティッキング性が得られる。
【００２６】
また、有機樹脂エマルジョン（ｂ２）の樹脂粒子径が０．６μｍ未満では耐スティッキング性が劣り、一方、１．５μｍ超では十分な耐食性が得られず、また耐スティッキング性も劣る傾向がある。また、特に優れた耐食性と耐スティッキング性が必要とされる場合には、有機樹脂エマルジョン（ｂ２）の樹脂粒子径は０．６〜１．０μｍとすることが望ましい。
【００２７】
上記有機樹脂エマルジョン（ｂ１）と有機樹脂エマルジョン（ｂ２）の処理液中での配合量は、ＣｒＯ３換算量での無機成分（ａ）１００重量部に対して樹脂固形分の合計で２０〜５０重量部とする。有機樹脂エマルジョン（ｂ１）と有機樹脂エマルジョン（ｂ２）の合計の配合量が２０重量部未満では、これら複合添加される有機樹脂エマルジョンによる耐スティッキング性、耐食性および密着性の改善効果が十分に得られず、また、皮膜中での有機樹脂の割合も少なくなるため打ち抜き性も劣る。一方、配合量が５０重量部を超えると耐食性が劣化するため好ましくない。
【００２８】
また、有機樹脂エマルジョン（ｂ１）／有機樹脂エマルジョン（ｂ２）の樹脂固形分の配合比は、特に耐スティッキング性及び耐食性の観点から重量比で７０／３０〜９０／１０とする。この配合比が７０／３０未満（有機樹脂エマルジョン（ｂ２）の割合が３０％を超える）では耐食性及び耐スティッキング性が劣る傾向があり、一方、９０／１０を超える（有機樹脂エマルジョン（ｂ２）の割合が１０％未満）と耐スティキング性が劣る傾向があるため好ましくない。
【００２９】
また、処理液中に含まれる６価Ｃｒイオンを還元して皮膜を不溶化するために、処理液中に有機還元剤を添加することが好ましい。通常、有機還元剤としてはポリエチレングリコール、エチレングリコール、ショ糖等の多価アルコールが用いられる。この有機還元剤の配合量は、ＣｒＯ３換算量での無機成分（ａ）１００重量部に対して１０〜８０重量部とすることが好ましい。有機還元剤の配合量が１０重量部未満では未還元の６価Ｃｒイオンが残存するため皮膜の耐水性が劣り、一方、８０重量部を超えると処理液中で還元反応が進行し、処理液がゲル化してしまう。
【００３０】
また、処理液中に硼酸及び／又は硼酸塩を添加すると耐スティッキング性がさらに向上するため好ましい。この硼酸及び／又は硼酸塩の合計の配合量は、ＣｒＯ３換算量での無機成分（ａ）１００重量部に対して５〜６０重量部とすることが好ましい。硼酸及び／又は硼酸塩の合計の配合量が５重量部未満では耐スティッキング性の改善効果が十分に得られず、一方、６０重量部を超えると耐食性が劣化するため好ましくない。
【００３１】
また、処理液中には以上述べた主成分の他に、皮膜の耐食性や耐熱性等の向上を目的としてＭｇ、Ｃａ、Ａｌ又はＺｎのリン酸塩の１種又は２種以上、シリカ等の酸化物等の１種又は２種以上を配合することができ、これら添加成分の合計の配合量がＣｒＯ３換算量での無機成分（ａ）１００重量部に対して２０重量部以下であれば本発明の基本的な効果には何ら影響はない。
【００３２】
本発明の電磁鋼板の絶縁皮膜は、上記の処理液を鋼板表面に塗布し、焼付することにより形成される。絶縁皮膜の膜厚は０．２μｍ〜２．０μｍとする。本発明の効果は、特に絶縁皮膜の膜厚が０．６〜０．５μｍ以下の薄膜の場合においても問題なく得られるという利点がある。本発明において絶縁皮膜の膜厚とは、電磁鋼板表面から皮膜の最表層までの平均的な厚さを指すが、皮膜に極端な凹凸のある場合は、電磁鋼板表面から皮膜最表層の凸部までの厚さと電磁鋼板表面から皮膜最表層の凹部までの厚さの平均値とする。
【００３３】
絶縁皮膜の膜厚が０．２μｍ未満では絶縁性、耐スティッキング性、耐食性が劣り、一方、膜厚が２．０μｍを超えると占積率や溶接性が劣る。特に好ましい膜厚は０．３〜１．０μｍである。
なお、絶縁皮膜の形成方法は、通常、上記処理液をロールコーター等で電磁鋼板表面に塗布した後、熱風乾燥炉やインダクションヒーターで焼き付ける方法が採られる。
【００３４】
【実施例】
表１〜表６に示す絶縁皮膜形成用の処理液（Ｎｏ．１〜Ｎｏ．４１）を調整した。これらの処理液は、無水クロム酸の水溶液にＭｇＯを溶解した無機系水溶液（さらに、Ｎｏ．２７以外は硼酸も含む）に対して表１〜表６に示す有機樹脂エマルジョンを添加して調整した。これら処理液を板厚０．５ｍｍの電磁鋼板の表面に所定膜厚になるようにロールコーターにより塗布した後、到達板温２８０℃で焼き付け、絶縁皮膜を形成した。
このようにして得られた電磁鋼板について、耐スティッキング性、耐食性、皮膜密着性、耐臭気性、打ち抜き性を評価するため下記の試験を行なった。その結果を表７〜表９に示す。
【００３５】
（ａ）耐スティッキング性
鋼板を４８ｍｍφに打ち抜いてこれを１１枚積層し、締め付け圧力４０ｋｇｆ／ｃｍ２で締め付けた状態で焼鈍（８００℃×２時間、Ｎ２ガス雰囲気中）を行った。焼鈍後、締め付けを解除し、板／板間の何箇所でスティックが生じているかを調べ、スティック発生箇所の数で耐スティッキング性を評価した。その評価基準は以下の通りである。
◎ ：スティック発生０箇所
○＋：スティック発生１〜２箇所
○ ：スティック発生３〜４箇所
△ ：スティック発生５〜７箇所
× ：スティック発生８箇所以上
【００３６】
（ｂ）耐食性
鋼板を７０ｍｍ×１５０ｍｍのサイズに剪断し、この供試材の裏面及びエッジ部をシールした後、塩水噴霧試験を１５時間行ない、試験後の赤錆発生面積率により耐食性を評価した。その評価基準は以下の通りである。
◎：赤錆発生面積率２０％以下
○：赤錆発生面積率２０％超、４０％以下
△：赤錆発生面積率４０％超、６０％以下
×：赤錆発生面積率６０％超
【００３７】
（ｃ）皮膜密着性
（１）歪取焼鈍無し
供試材に１０ｍｍφの曲げ加工を施した後、その曲げ部にテープ剥離試験を実施し、テープへの剥離皮膜の有無を目視で判定することにより皮膜密着性を評価した。
（２）歪取焼鈍有り
歪取り焼鈍（７５０℃×２時間、Ｎ２ガス雰囲気中）を施した供試材に１０ｍｍφの曲げ加工を施した後、その曲げ部にテープ剥離試験を実施し、テープへの剥離皮膜の有無を目視で判定することにより皮膜密着性を評価した。
これらの試験による評価基準は以下の通りである。
（ｄ）耐臭気性
供試材を打抜き後、積層し、この積層体の端面をＴＩＧ溶接し、その際に発生する臭気（溶接ガス）の程度を１０名の評価者により評価した。その評価基準は以下の通りである。
◎：不快臭を感じた人０名
○：不快臭を感じた人１名〜３名
△：不快臭を感じた人４名〜５名
×：不快臭を感じた人６名以上
【００３９】
（ｅ）打ち抜き性
金型材質ＳＫＤ−１の角型ダイスを用い、クリアランス６％で軽油系の打抜油を使用して連続打ち抜き試験を行い、かえり高さが５０μｍに達するまでの打抜き回数を調べた。
【００４０】
【表１】
【表２】
【表３】
【表４】
【表５】
【表６】
【表７】
【表８】
【表９】
【発明の効果】
以上述べた本発明の電磁鋼板によれば、耐食性及び耐スティッキング性がともに優れ、しかも、皮膜密着性、耐臭気性、打ち抜き性等の特性も良好である。また、特に０．６〜０．５μｍ以下の薄膜の絶縁被膜を形成した場合にも優れた耐スティッキング性と耐食性が得られる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electromagnetic steel sheet having an insulating film on a surface, which is mainly used as an iron core material of a motor, a transformer, and the like.
[0002]
[Prior art]
Electromagnetic steel sheets are widely used as iron core materials for motors and transformers, and are usually used by coating the steel sheet surface with an insulating film for reducing eddy current loss.
Many iron cores, such as motors and transformers, are manufactured by punching or shearing electromagnetic steel sheets with an insulating film into a predetermined shape, and then laminating them.The laminate is fixed by welding or caulking, and strain is removed as necessary. After annealing, the product is wound and wound into a product.
[0003]
The insulating film of the electromagnetic steel sheet, which is a material for such an iron core, is required to have not only high insulation properties but also excellent film adhesion, weldability, corrosion resistance, punching property and the like. Further, when the strain relief annealing is performed, when the steel sheets adhere to each other during the annealing (sticking), an electric short circuit occurs, and a problem of increasing iron loss occurs. Therefore, the steel sheets do not adhere during the annealing, that is, Excellent sticking resistance is required.
[0004]
Conventionally, the following techniques have been proposed in order to obtain such various characteristics.
JP-A-3-240970 discloses a method for producing an electrical steel sheet having excellent film properties (seizure resistance and lubricity) after strain relief annealing, including chromic acid, oxides such as Al and Mg, and resin particle diameter. Is an organic resin emulsion of 0.2 to 0.5 μm (acrylic, styrene, vinyl acetate and / or a copolymer resin thereof) and an organic resin emulsion having a resin particle diameter of 1 to 50 μm (methyl methacrylate, polyacrylonitrile, A method of forming an insulating film by applying a treatment liquid composed of a resin such as polystyrene and / or a copolymer resin thereof or a crosslinked resin) to the surface of an electromagnetic steel sheet and baking the same is disclosed.
[0005]
Patent No. 2662148 discloses that one or two or more of epoxy, styrene, phenol, melamine, polyester, vinyl acetate, acrylic, and silicone emulsion resins having a resin particle diameter of 0.5 to 3.0 μm are provided on the surface of an electromagnetic steel sheet. And a treatment agent containing one or more of the chromates of Al, Mg, Ca and Zn as a main component is applied and baked to form an insulating film having a surface roughness Ra of 0.15 to 0.6 μm. Further, there is disclosed a non-oriented electrical steel sheet which is excellent in film characteristics and has a spherical projection formed on the surface by an emulsion resin having a diameter of 3 μm or less and a height of 3 μm or less.
[0006]
[Problems to be solved by the invention]
However, these conventional techniques have the following problems.
Japanese Patent Application Laid-Open No. 3-240970 discloses a technique in which, in addition to resin fine particles having a particle diameter of 0.2 to 0.5 μm as an organic resin emulsion, coarse resin particles having a large particle diameter (substantially, Resin particles having a particle diameter of several μm or more). For this reason, although the sticking resistance is improved by the added coarse resin particles, the corrosion resistance in a severe corrosive environment where chloride ions are present is inferior. Further, there is also a problem that the film characteristics are not stable due to the aggregation of the resin particles due to the addition of the coarse resin particles and the unevenness of the resin particles in the film.
[0007]
In the technique of Japanese Patent No. 2662148, an organic resin emulsion having a particle diameter of 0.5 to 3.0 μm is used alone in order to give a predetermined surface shape to the insulating film. In the case of a thin film having a thickness of 5 to 0.6 μm or less, resin particles are missing and hardly contained in the film. As a result, the effect of anti-sticking property expected by the resin particles is reduced, and rust is formed in the missing portion. Are likely to occur, and the corrosion resistance becomes extremely poor. In particular, in recent years, insulating films have tended to be thinner from the viewpoint of increasing the efficiency of motors and the like, and in such thin insulating films, sufficient sticking resistance and corrosion resistance cannot be obtained by the technique of Patent No. 2662148. I can't get it.
[0008]
Accordingly, an object of the present invention is to provide an electromagnetic steel sheet having an insulating film excellent in both sticking resistance and corrosion resistance, and also excellent in various other properties required as an insulating film, in particular, 0.5 to 0.6 μm or less. An object of the present invention is to provide an electromagnetic steel sheet which can obtain excellent sticking resistance and corrosion resistance even when a thin insulating film is formed.
[0009]
[Means for Solving the Problems]
The present inventors focused on the resin particle size of the organic resin emulsion blended with the inorganic component when forming the inorganic-organic insulating film, and conditions for obtaining an insulating film excellent in both sticking resistance and corrosion resistance. Various experiments and examinations were carried out on, and as a result, the following findings were obtained.
[0010]
(1) Increasing the resin particle diameter of the organic resin emulsion dispersed in the insulating film improves the sticking resistance, but on the other hand, the corrosion resistance deteriorates as the resin particle diameter increases.
(2) To solve such a problem, as an organic resin emulsion dispersed in an insulating film, a composite of a fine particle organic resin emulsion having a specific particle diameter and an organic resin emulsion having a specific particle diameter larger than this is used. By adding, an insulating film excellent in both sticking resistance and corrosion resistance can be obtained.
[0011]
(3) When these two kinds of organic resin emulsions to be added in combination are blended in a specific ratio, particularly excellent sticking resistance and corrosion resistance can be obtained.
(4) By optimizing the ratio of the inorganic component and the organic component in the insulating film and adding boric acid and / or borate as a part of the inorganic component, the sticking resistance and the corrosion resistance are further improved.
The present invention has been made based on such knowledge, and is characterized by having the following configuration.
[0012]
[1] At least one selected from chromic anhydride, chromate, and bichromate, and oxides, hydroxides and carbonates of divalent or trivalent metals on the surface of an electrical steel sheet. And an inorganic aqueous solution (a) containing at least one selected from the group consisting of an epoxy resin, a styrene resin, a phenol resin, a melamine resin, a polyester resin, a vinyl acetate resin, a veoba resin, an acrylic resin, and silicone. An organic resin emulsion (b1) comprising one or more resin emulsions selected from the resin emulsions of the respective series and having a resin particle diameter of 0.01 to 0.14 μm, an epoxy resin, a styrene resin, and phenol Resin resin, melamine resin, polyester resin, vinyl acetate resin, veova resin, acrylic resin, silicone resin Consists species or two or more, diameter resin particles as a main component and an organic resin emulsion (b2) is 0.6-1.5, and an organic resin emulsion (b 1) with an organic resin emulsion (b 2) The compounding ratio of the resin solid content is, in terms of weight ratio, organic resin emulsion (b 1 ) / organic resin emulsion (b 2 ) = 70/30 to 90/10, relative to 100 parts by weight of inorganic component (a) in terms of CrO 3 . A film thickness of 0 formed by applying and baking a treatment liquid in which the total amount of the organic resin emulsion (b 1 ) and the organic resin emulsion (b 2 ) in the resin solid content is adjusted to 20 to 50 parts by weight. An electrical steel sheet having excellent sticking resistance and corrosion resistance, characterized by having an insulating film of 0.2 to 2.0 μm.
[0013]
[2] At least one selected from chromic anhydride, chromate, and bichromate, and oxides, hydroxides and carbonates of divalent or trivalent metals on the surface of the magnetic steel sheet. And an inorganic aqueous solution (a) containing at least one selected from the group consisting of an epoxy resin, a styrene resin, a phenol resin, a melamine resin, a polyester resin, a vinyl acetate resin, a veoba resin, an acrylic resin, and silicone. An organic resin emulsion (b1) comprising one or more resin emulsions selected from the resin emulsions of the respective series and having a resin particle diameter of 0.01 to 0.14 μm, an epoxy resin, a styrene resin, and phenol Resin resin, melamine resin, polyester resin, vinyl acetate resin, veova resin, acrylic resin, silicone resin Consists species or two or more, and an organic resin emulsion size resin particles are 0.6-1.5 (b2), and boric acid and / or borate, mainly composed of an organic reducing agent, and an organic resin emulsion The compounding ratio of the resin solid content of (b 1 ) and the organic resin emulsion (b 2 ) is such that the weight ratio of the organic resin emulsion (b 1 ) / the organic resin emulsion (b 2 ) = 70/30 to 90/10, CrO 3 The total amount of the organic resin emulsion (b1) and the organic resin emulsion (b2) in terms of the resin solid content relative to 100 parts by weight of the inorganic component (a) is 20 to 50 parts by weight of boric acid and / or borate. Insulation having a film thickness of 0.2 to 2.0 μm formed by applying and baking a processing solution adjusted to a total amount of 5 to 60 parts by weight and an organic reducing agent of 10 to 80 parts by weight. Has a coating Excellent electromagnetic steel sheet sticking resistance and corrosion resistance, characterized in that.
[0014]
[3] The electromagnetic steel sheet according to [1] or [2], wherein the organic resin emulsion (b2) has a resin particle diameter of 0.6 to 1.0 μm, and is excellent in sticking resistance and corrosion resistance. steel sheet.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the details of the present invention will be described together with the reasons for limitation.
In the present invention, the steel sheet serving as the substrate on which the insulating film is formed is an electromagnetic steel sheet for an iron core used for electric equipment such as a motor and a transformer. As such electrical steel sheets, non-oriented electrical steel sheets and grain-oriented electrical steel sheets are generally used, but other than these, mild steel sheets, stainless steel sheets, other special steel sheets, etc. may be used, and the steel sheets serving as substrates are not particularly limited. Not done. The effect of the present invention can be obtained even when any of these steel plates is used as the substrate.
[0017]
Further, the magnetic steel sheet serving as the substrate may be one in which one or two or more kinds of surface treatment such as zinc-based plating or other metal plating film, chemical conversion coating film, etc. have been applied to the surface thereof. The term “surface” refers to the surface of the uppermost film when these surface treatment films are provided.
[0018]
The insulating film formed on the surface of the magnetic steel sheet of the present invention is formed of at least one selected from chromic anhydride, chromate, and dichromate, and a divalent or trivalent metal oxide, Organic resin comprising one or more specific resin emulsions having a resin particle diameter of 0.01 to 0.14 μm in an inorganic aqueous solution (a) containing at least one selected from a substance and a carbonate. Emulsion (b1), an organic resin emulsion (b2) composed of one or more specific resin emulsions having a resin particle diameter of 0.6 to 1.5 μm, and further, if necessary, boric acid and / or This is a film formed by applying and baking a treatment liquid containing a borate and an organic reducing agent.
[0019]
The inorganic aqueous solution (a) in the treatment liquid contains at least one selected from chromic anhydride, chromate, and dichromate, and oxides, hydroxides, and carbonates of divalent or trivalent metals. It is an inorganic aqueous solution containing at least one selected from salts.
As the chromate and the dichromate, salts of sodium, potassium, magnesium, calcium, manganese, molybdenum, zinc, aluminum and the like can be used.
[0020]
Examples of the divalent or trivalent metal oxide dissolved in the aqueous solution include, for example, MgO, CaO, and ZnO, and the hydroxides include Mg (OH) 2 , Ca (OH) 2 , and Zn (OH). 2 and the like, carbonates include MgCO 3 , CaCO 3 , ZnCO 3 and the like. These are dissolved in an aqueous solution using at least one of chromic anhydride, chromate, and bichromate as a main agent, Inorganic aqueous solution.
An inorganic-organic insulating film containing a chromium compound can be formed by these inorganic components.
[0021]
An organic resin emulsion (b1) and an organic resin emulsion (b2) having different resin particle diameters are blended in the treatment liquid containing the inorganic component.
The organic resin emulsion (b1) is a resin emulsion of epoxy resin, styrene resin, phenol resin, melamine resin, polyester resin, vinyl acetate resin, veoba resin, acrylic resin, and silicone resin. A resin emulsion of one or more selected from the group and having a resin particle diameter of 0.01 to 0.14 μm; and the organic resin emulsion (b2) is an epoxy resin, a styrene resin, A resin particle diameter of one or more selected from resin emulsions of phenolic resin, melamine resin, polyester resin, vinyl acetate resin, veoba resin, acrylic resin, and silicon resin. Is a resin emulsion of 0.6 to 1.5 μm. The present invention is greatly characterized in that two kinds of organic resin emulsions having different specific particle sizes having different sizes are added in combination.
[0022]
When the above-mentioned organic resin emulsion (b1) is used alone as the resin emulsion, the physical effect due to the unevenness of the organic resin itself in the insulating film is not obtained at the time of strain relief annealing after lamination, and the original plate itself at the time of strain relief annealing is not obtained. The stress concentrates only on the convex portions caused by the roughness of the insulating film, and the stress concentration and the heat at the time of annealing destroy the insulating film and cause sticking. On the other hand, when the organic resin emulsion (b2) is used alone as the resin emulsion, particularly when the thickness of the insulating film is 0.5 to 0.6 μm or less, the resin particles are less likely to be taken into the film, and The effect of improving the anti-sticking property expected from the resin emulsion (b2) is remarkably reduced, and even if the resin particles of the organic resin emulsion (b2) are incorporated into the film, the particles are easily missing, so that a film defect portion is formed. Occurs, and as a result, the corrosion resistance and the insulation are reduced.
[0023]
On the other hand, when the organic resin emulsion (b1) and the organic resin emulsion (b2) are added in combination, an insulating film excellent in both sticking resistance and corrosion resistance can be obtained. The reason why excellent characteristics can be obtained by adding two kinds of organic resin emulsions having specific particle diameters different in size in this manner is not necessarily clear, but the organic resin emulsion (b1) can be used together with the organic resin emulsion (b1). It is considered that this is because the emulsion (b2) is easily taken into the film.
[0024]
The organic resin emulsion (b1) and the organic resin emulsion (b2) are epoxy resin, styrene resin, phenol resin, melamine resin, polyester resin, vinyl acetate resin, veova resin, acrylic resin, and silicon resin. One or more resin emulsions selected from resin emulsions. Other organic resin emulsions have poor stability in a chromic acid-based inorganic aqueous solution, so they deteriorate a short time after being mixed in the aqueous solution, causing gel-like bumps and gelling of the entire processing solution, It is not preferable because of practical problems.
[0025]
When the resin particle diameter of the organic resin emulsion (b1) exceeds 0.14 μm , the effect of incorporating the resin particles of the organic resin emulsion (b2) into the film is sufficiently obtained when forming the above-mentioned thin insulating film. Therefore, sticking resistance and corrosion resistance are inferior. The more preferable resin particle diameter of the organic resin emulsion (b1) is 0.01 to 0.14 μm , whereby particularly excellent sticking resistance is obtained.
[0026]
When the resin particle diameter of the organic resin emulsion (b2) is less than 0.6 μm , the sticking resistance is poor. On the other hand, when the resin particle diameter is more than 1.5 μm , sufficient corrosion resistance cannot be obtained and the sticking resistance tends to be poor. Further, when particularly excellent corrosion resistance and sticking resistance are required, the resin particle diameter of the organic resin emulsion (b2) is desirably 0.6 to 1.0 μm .
[0027]
The compounding amount of the organic resin emulsion (b1) and the organic resin emulsion (b2) in the treatment liquid is 20 to 50 in total of the resin solid content with respect to 100 parts by weight of the inorganic component (a) in terms of CrO 3. Parts by weight. When the total amount of the organic resin emulsion (b1) and the organic resin emulsion (b2) is less than 20 parts by weight , the effect of improving the sticking resistance, corrosion resistance and adhesion by the composite resin emulsion can be sufficiently obtained. In addition, since the proportion of the organic resin in the film is reduced, the punching property is also poor. On the other hand, undesirable because corrosion resistance is deteriorated if the amount exceeds 50 parts by weight.
[0028]
Further, the mixing ratio of the resin solid content of the organic resin emulsion (b1) / the organic resin emulsion (b2) is set to 70/30 to 90/10 by weight, particularly from the viewpoint of sticking resistance and corrosion resistance . When the compounding ratio is less than 70/30 (the ratio of the organic resin emulsion (b2) exceeds 30% ), the corrosion resistance and the sticking resistance tend to be inferior, while the compounding ratio exceeds 90/10 (the organic resin emulsion (b2) undesirable because the ratio tends to be inferior less than 10%) and anti-sticking property.
[0029]
Further, in order to reduce hexavalent Cr ions contained in the treatment liquid to insolubilize the film, it is preferable to add an organic reducing agent to the treatment liquid. Usually, polyhydric alcohols such as polyethylene glycol, ethylene glycol, and sucrose are used as the organic reducing agent. The amount of the organic reducing agent is preferably 10 to 80 parts by weight based on 100 parts by weight of the inorganic component (a) in terms of CrO 3 . If the compounding amount of the organic reducing agent is less than 10 parts by weight, unreduced hexavalent Cr ions remain, so that the water resistance of the film is poor. On the other hand, if it exceeds 80 parts by weight, the reduction reaction proceeds in the processing solution, Will gel.
[0030]
Further, it is preferable to add boric acid and / or borate to the treatment liquid, because sticking resistance is further improved. The total amount of boric acid and / or boric acid salt is preferably an inorganic component (a). 5 to 60 parts by weight per 100 parts by weight of at CrO 3 equivalent amount. If the total amount of boric acid and / or borate is less than 5 parts by weight, the effect of improving the sticking resistance cannot be sufficiently obtained, while if it exceeds 60 parts by weight , the corrosion resistance is undesirably deteriorated.
[0031]
In addition, in the treatment liquid, in addition to the main components described above, one or more of Mg, Ca, Al or Zn phosphates for the purpose of improving the corrosion resistance and heat resistance of the coating, such as silica. One or more kinds of oxides and the like can be compounded. If the total amount of these additional components is 20 parts by weight or less based on 100 parts by weight of the inorganic component (a) in terms of CrO 3. There is no effect on the basic effects of the present invention.
[0032]
The insulating film of the magnetic steel sheet of the present invention is formed by applying the above-described treatment liquid to the surface of the steel sheet and baking it. The thickness of the insulating film is 0.2 μm to 2.0 μm. The effect of the present invention has an advantage that it can be obtained without any problem even when the thickness of the insulating film is 0.6 to 0.5 μm or less. In the present invention, the thickness of the insulating film refers to the average thickness from the surface of the electromagnetic steel sheet to the outermost layer of the film. And the average of the thickness from the surface of the electromagnetic steel sheet to the concave portion of the outermost layer of the coating.
[0033]
If the thickness of the insulating film is less than 0.2 μm, the insulation, sticking resistance, and corrosion resistance are poor. On the other hand, if the thickness exceeds 2.0 μm, the space factor and weldability are poor. A particularly preferred film thickness is 0.3 to 1.0 μm.
In addition, as a method for forming an insulating film, a method is usually employed in which the above-mentioned treatment liquid is applied to the surface of a magnetic steel sheet using a roll coater or the like and then baked in a hot-air drying furnace or an induction heater.
[0034]
【Example】
Processing solutions (No. 1 to No. 41) for forming an insulating film shown in Tables 1 to 6 were prepared. These treatment liquids were prepared by adding the organic resin emulsions shown in Tables 1 to 6 to an inorganic aqueous solution in which MgO was dissolved in an aqueous solution of chromic anhydride (furthermore, boric acid was included except for No. 27). . These treatment liquids were applied to the surface of an electromagnetic steel sheet having a sheet thickness of 0.5 mm by a roll coater so as to have a predetermined film thickness, and then baked at a sheet temperature of 280 ° C. to form an insulating film.
The following tests were performed on the magnetic steel sheets thus obtained in order to evaluate sticking resistance, corrosion resistance, film adhesion, odor resistance, and punching properties. Tables 7 to 9 show the results.
[0035]
(A) An anti-sticking steel plate was punched out to a diameter of 48 mm, 11 of these were stacked, and annealed (800 ° C. × 2 hours in an N 2 gas atmosphere) while being tightened at a tightening pressure of 40 kgf / cm 2 . After the annealing, the tightening was released, the number of sticks between the plates was examined, and the sticking resistance was evaluated by the number of sticks. The evaluation criteria are as follows.
: 0 stick occurrences ○ +: 1 to 2 stick occurrences 〜: 3 to 4 stick occurrences △: 5 to 7 stick occurrences X: 8 or more stick occurrences
(B) Corrosion resistance The steel sheet was sheared to a size of 70 mm x 150 mm, and after sealing the back surface and the edge of the test material, a salt spray test was performed for 15 hours, and the corrosion resistance was evaluated based on the red rust generation area ratio after the test. The evaluation criteria are as follows.
：: Red rust generation area ratio 20% or less ○: Red rust generation area ratio 20% or more, 40% or less Δ: Red rust generation area rate 40% or more, 60% or less ×: Red rust generation area rate 60% or more
(C) Film adhesion (1) Without strain relief annealing After subjecting the test material to a bending process of 10 mmφ, perform a tape peeling test on the bent part and visually determine the presence or absence of a peeling film on the tape. Was used to evaluate the film adhesion.
(2) With strain relief annealing After subjecting the test material subjected to the strain relief annealing (750 ° C. × 2 hours, N 2 gas atmosphere) to a bending process of 10 mmφ, a tape peeling test was performed on the bent portion, The film adhesion was evaluated by visually determining the presence or absence of a release film on the tape.
The evaluation criteria for these tests are as follows.
(D) Odor-resistant test materials were punched out, laminated, and the end faces of the laminate were subjected to TIG welding, and the degree of odor (welding gas) generated at that time was evaluated by ten evaluators. The evaluation criteria are as follows.
◎: 0 people who felt an unpleasant odor ○: 1 to 3 people who felt an unpleasant odor △: 4 to 5 people who felt an unpleasant odor ×: 6 or more people who felt an unpleasant odor
(E) Punching performance Using a square die of mold material SKD-1 and a continuous punching test using a light oil-based punching oil with a clearance of 6%, check the number of punching until the burr height reaches 50 μm. Was.
[0040]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
[Table 5]
[Table 6]
[Table 7]
[Table 8]
[Table 9]
【The invention's effect】
According to the magnetic steel sheet of the present invention described above, corrosion resistance and sticking resistance are both excellent, and characteristics such as film adhesion, odor resistance, and punching property are also good. In addition, even when a thin insulating film having a thickness of 0.6 to 0.5 μm or less is formed, excellent sticking resistance and corrosion resistance can be obtained.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12397098A JP3572938B2 (en) | 1998-04-17 | 1998-04-17 | Electrical steel sheet with excellent sticking and corrosion resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12397098A JP3572938B2 (en) | 1998-04-17 | 1998-04-17 | Electrical steel sheet with excellent sticking and corrosion resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11307333A JPH11307333A (en) | 1999-11-05 |
| JP3572938B2 true JP3572938B2 (en) | 2004-10-06 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12397098A Expired - Fee Related JP3572938B2 (en) | 1998-04-17 | 1998-04-17 | Electrical steel sheet with excellent sticking and corrosion resistance |
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| JP (1) | JP3572938B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4112866B2 (en) * | 2002-01-16 | 2008-07-02 | 新日本製鐵株式会社 | Non-oriented electrical steel sheet with excellent coating performance |
| JP4460312B2 (en) * | 2003-04-10 | 2010-05-12 | 新日本製鐵株式会社 | Non-oriented electrical steel sheet with excellent coating performance, insulating coating treatment agent, and insulating coating treatment method |
| KR101641757B1 (en) * | 2011-10-19 | 2016-07-21 | 후루카와 덴키 고교 가부시키가이샤 | Insulating coating material, insulated wire, and method for producing insulated wire |
| JP6984998B2 (en) * | 2016-04-27 | 2021-12-22 | 日本製鉄株式会社 | Non-oriented electrical steel sheets for high-performance motors |
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